The present invention relates to electronic devices.
It is generally recognized that conventional VLSI integrated technical technology will be prevented from further scaling by the time MOS devices get down to a quarter micron channel length, and perhaps even at much larger geometries. Since much of the advance in integrated circuit capabilities has been based on the continued progress of scaling, this near-future barrier is of substantial concern.
Thus it is an object of the present invention to provide an integrated circuit technology wherein active devices can have active regions smaller than one quarter micron in dimension.
It is further object of the present invention to provide an integrated circuit technology wherein active devices can be fabricated which occupy a total area of less than 1/4 of a square micron average for each active device.
A further inherent limitation of conventional integrated circuit technology is speed. MOS devices have inherent limits on their speed due to the channel-length transit time. Intergrable bipolar devices also have inherent speed limitations, due to the base width transit time, and are also likely to have high power dissipation.
Thus it is an object of the present invention to provide an active device having higher potential maximum speed than any MOS device.
It is a further object of the present invention to provide an active device which is potentially faster than any bipolar device.
It is a further object of the present invention to provide an active device which is potentially faster than any bipolar device, and which also has a very low power dissipation.
To achieve these and other objects, the present invention provides: a new genus of electronic devices, wherein at least two closely adjacent potential wells (e.g. islands of GaAs in an AlGaAs lattice) are made small enough that at least two components of momentum of carriers within the wells are discretely quantized. This means that, when the bias between the wells is adjusted to align energy levels of the two wells, tunneling will occur very rapidly, whereas when energy levels are not aligned, tunneling will be greatly reduced. This high-gain mechanism leads to useful electronic device functions.
A difficulty in making quantum-coupled devices into functional electronic circuits is that these devices are so extremely small that it is typically necessary to run a number of them in parallel to provide macroscopic output currents. In addition, the routing of wiring to couple into and out of these multiple parallel active devices is also difficult, since the tight geometry constraints of the devices place substantial constraints on the geometry which must be used for the wiring.
Thus, if these novel quantum devices are to be used to configure logic, it would be preferable to do so in such a way that the number of points where translation from quantum-well logic levels (which are essentially single-carrier or few-carrier transitions, all of these transitions may occur very rapidly) to macroscopic currents (those normally used in integrated circuits) is minimized, since these transitions lose some of the density and speed economy of the quantum coupled devices.
Thus it is an object of the present invention to provide an electronic logic structure in which logic functions can be embodied entirely in quantum-coupled devices, without intermediate stages using macroscopic currents.
It is a further object of the present invention to provide an electronic logic wherein all Boolean primitive logic functions can be embodied entirely in quantum-coupled devices, without intermediate stages using macroscopic currents.
It is an object of the present invention to provide an electronic logic family wherein numerous logic functions, including exceedingly complex logic functions, can be embodied entirely in quantum-coupled devices, without intermediate stages using macroscopic currents.
According to the present invention there is provided:
An electronic device comprising:
first and second potential wells each comprising an island if a semiconducting material, said first and second wells being sufficiently small in all three dimensions that energy levels within each of said wells are separated by more than one half millielectronVolt;
a barrier medium, interposed between said first and second wells, wherein the minimum potential energy of carriers is higher than the minimum potential energy of carriers within said wells;
said wells being physically separated by a distance which is less than 300 Angstroms;
means for inputting carriers into said first well;
means for removing carriers from said second well;
said energy levels of said wells being such that, under a first bias condition, at least one of the five lowest-lying discrete energy and momentum states in said first well is aligned with a discrete state in a said second well if and only if the difference between the number of occupied states in said first well and the number of occupied states in said second well is a predetermined number.